1. Field of the Invention
This invention relates to processes for preparing food products from plant seeds for feeding to young mammals and certain older mammals, to products prepared by the processes and to foods incorporating such food products.
While terms such as "feed" and "feedstuff" are often used to describe foods given to farm livestock and non-human mammals the term "food" can be applied equally to food given to such animals and to man so that when the terms "food product", "product" or "foodstuff" are ued in this Specification, they are to be taken as generally meaning, depending on the context, a food ingredient or food which can be used in the feeding of non-human mammals and of humans.
The products of the process according to the present invention find particular application in the feeding of young farm animals, especially young ruminants such as calves and lambs, and pigs, but the use of such products is not restricted exclusively to the feeding of young farm animals since they also find application in the feeding of other young mammals such as the human infant, domestic pets such as the dog and the cat and certain older animals as described hereinafter.
Young ruminants, such as the young of cattle, sheep and goats, namely the calf, lamb and kid respectively, naturally depend on mother's milk to provide nourishment during the period when, because rumen and other digestive functions are not adequately developed, such animals are unable to utilise the foodstuffs consumed by adult animals of these species. This period encompasses the stage during which the young animals are in the pre-ruminant stage, i.e., when their digestive functions are more akin to those of monogastric animals, and also the subsequent period during which rumen function is developing, but is not yet capable of fully catering for the animal's normal needs. In modern dairy husbandry, it is now common practice to take the calf away from the cow at birth or within several days of birth and to rear the calf independently of its mother's milk by providing a substitute (i.e., milk-replacer) for mother's milk. In the case of calves, intended as replacement animals for the dairy and beef herds, which may have free access to concentrate feed mixtures and roughage such as hay, the period from birth to about three weeks of age is generally regarded as the preruminant stage, while subsequently during the period of developing rumen function, the animal is regarded as being dependent on supply of mother's milk or milk-replacer until about the age of six or seven weeks. The term "young ruminant" will therefore be applied to this type of animal to cover the period from birth until about six or seven weeks of age. In the case of the veal calf, however, concentrate feed mixtures and roughage are not usually provided so that the animal is dependent on the provision of mother's milk or milk-replacer from birth until thirteen to fourteen weeks of age or more, and during this time it is regarded as being in the preruminant stage since, because of the dietary regimen, its rumen function does not develop in the usual way. Consequently the term "young ruminant" will also be used for this type of animal to include replacement and veal calves.
Because of the high cost and inconvenience of feeding liquid cow's milk, dried skim milk powder manufactured from cow's milk has become the principal ingredient of milk-replacers for calves and other young ruminants. Dried skim milk possesses important physico-chemical properties which have proved necessary for this type of application, such as dispersibility, solubility, suspensibility in aqueous liquid and fat-binding ability, and has favourable characteristics of colour, taste and smell. Thus dried skim milk can provide the major source of protein suitable for the young ruminant, whose requirements in terms of protein-amino acid balance, digestibility and availability appear to be most exacting. At the same time dried skim milk is an important source of energy, providing the milk sugar lactose, which in moderate amounts is well utilised by the young ruminant. Accordingly dried skim milk combined with suitable fats, minerals and vitamins and when reconstituted with water has been demonstrated in practice to meet adequately the rather critical requirements of young ruminants.
However, skim milk powder has been relatively scarce on the world market, its cost has increased sharply in recent years and economic projections suggest that this situation will continue or worsen in the foreseeable future. The situation has been exacerbated by increasing demand for the material as an ingredient for human foods. There have thus been strong incentives to find alternatives to skim milk powder. For example, efforts have been made to develop products from soybean meal, from fishery by-products, such as fish meal, and from microbial sources such as yeasts, to provide substitute protein sources for calf feeding. However, it has not been a simple matter to devise suitable products, at an economical price, which have the desired properties for inclusion in milk-replacers. In particular, problems have occurred with respect to solubility and suspensibility when combined with water; with particle size and digestibility; with digestive upsets and adverse clinical reactions; and with inadequate growth and feed-conversion efficiency.
Certain animal fats and vegetable oils are employed as energy sources in calf foods, but it is not possible to use carbohydrates such as sources and starch as energy sources to any great extent to replace lactose because of the calf's inability to digest such materials and its intolerance to them in the early weeks of its life. This is because, as has been demonstrated in the scientific literature, enzymes which hydrolyse sucrose and starch to simple sugars readily absorbed by the digestive tract are present only in small amounts in the digestive tracts of newly-born calves, lambs and other animals, apart from the enzyme, lactase, which specifically hydrolyses lactose. The amounts of such amylolytic or sucrase enzymes increase only gradually with age and development. In the case of starches and sucrose therefore, the inclusion of more than minimum amounts in milk-replacers also causes digestive upsets and lowered performance of calves. Thus, normally such economical energy sources as sucrose and starch-containing materials can be used only to a very limited extent in milk-replacers for calves.
Equally, the young ruminant is unable to digest and utilise plant fibre which is composed of lignin, cellulose and other related polysaccharides, so that a further limitation is imposed on plant protein sources such as soybeans or derived products.
Apart from the oleaginous seeds sometimes or oil seeds such as soybean and peanut, varieties of legume seeds such as beans, peas, lentils, chickpeas, cowpeas, grams and vetches contain high levels of good quality protein which in itself is well tolerated and utilised by young mammals particularly when supplemented with a small proportion of particular amino acids or complemented with appropriate proteins from other sources. The lipid content of such seeds although acceptable to the young mammal tends to be comparatively low. However, the high fibre level, residing mainly in the seed coat, and the high starch level of the cotyledon have made the use of such seeds undesirable for the feeding of young mammals for the reasons given above. Such seeds are distinctly different in composition from the oleaginous seeds, soybean and peanut, which are rich in oil and contain relatively low levels of starch. Such seeds also differ in composition from cereals such as wheat, oats, barley and milo which, although also rich in starch and fibre are relatively low in protein.
2. Description of Prior Art
Oleaginous seeds which contain high levels of unsaturated fatty acids are also likely to contain active enzymes which can act on such fatty acids during processing to produce most undesirable off-flavours and odours which render resulting products for food use unacceptable to the consumer. For example, it is well known in the case of soybeans that the enzyme, lipoxidase, becomes extremely active whenever soybeans are subjected to processing treatments such as hulling, grinding and slurrying in mild to moderate temperature conditions. The lipoxidase present acts on the unsaturated fatty acids present in soybeans to produce a very large number of lower molecular weight compounds, many of which have an unfavourable flavour impact. Resort has therefore had to be made to heat-treating soybeans before processing or simultaneously treating the soybeans with boiling water and grinding, with further high temperature heat-treatment of the resulting slurry, in an effort to minimise lipoxidase action. Such severe heat-treatments, of course, are likely to affect adversely the solubility and nutritive value of the protein, making the production of milk-replacer type products impossible or difficult. Further, when amylolytic enzymes are used on such substrates care must be taken to ensure that undesirable protease and/or lipoxidase activity is not present in such enzyme preparations which can, through protein hydrolysis, lead to the production of undesirable flavour factors and predispose to undesirable sugar/amino acid interactions and/or through lipoxidase activity lead to off-flavours and tastes as described previously. For this reason, the purity of the enzyme preparations employed must be carefully controlled as must the conditions in which they are allowed to operate. For such reasons too when protease preparations as such are introduced to promote protein breakdown for specific purposes as described in the present Specification, the source, purity and operating conditions of such preparations must be carefully controlled.
It is not apparent from the Specification of U.S. Pat. No. 3,258,407, which describes the extraction of alimentary values from vegetable tissues, that there are suitable provisions for dealing with the serious problems likely to be encountered in employing oleaginous seeds and vegetable tissues as starting materials for the proposed processes, while with the relatively crude enzyme sources employed, their sequence of use and the relatively mild temperature, intermediate pH and fairly long time conditions described in the Specification, there is every chance of producing preparations or products, which, from the points of view of nutritional value, flavour and taste, would be unacceptable.